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World won’t cool without geoengineering, warns report

By Fred Pearce

HALFWAY. We are halfway to dangerous climate change. That is the stark warning that concludes the draft summary of the latest climate assessment of the Intergovernmental Panel on Climate Change (IPCC) to be released on Friday.

As New Scientist went to press, the text was still being discussed by government representatives. According to one of its lead authors, the report will say that to limit global warming to 2°C, we must keep CO2 emissions from all human sources since the start of the Industrial Revolution to below about a trillion tonnes of carbon.

So far, we have emitted about half this amount. Human activities are emitting around 10.5 billion tonnes of carbon annually and rising, mostly as a result of burning fossil fuels.

The IPCC will also say that global warming is irreversible without massive geoengineering of the atmosphere’s chemistry. The latest draft, seen by New Scientist, states that even following “a complete cessation of emissions… carbon dioxide-induced warming is projected to remain approximately constant for many centuries. A large fraction of climate change is thus irreversible on a human timescale.” In other words, even if the world ran on carbon-free energy and we stopped deforestation, temperatures could only be lowered by removing large amounts of CO2 from the atmosphere. A conference in the UK this week is discussing the pros and cons of such geoengineering methods.

This article appeared in print under the headline “On the road to danger”